108 Dr. Naumann's Observations ofi the Porphi/ty t^ Toeplitz, 



logical varieties, in some of which it becomes so far removed 

 from bituminous wood and approaches coal, that it was long 

 considered as of the same species, and bore that name. It is 

 an important example of the too great influence mineralogical 

 characteis have been permitted to have on geology. In fact, 

 confining ourselves to the principal varieties, we find true an- 

 thracite in this carbonaceous mass, that is to say, a dense car- 

 bon without bitumen, sometimes with a dull, sometimes with 

 a shining fracture. We here find a thick bed of compact, 

 solid, fossil bituminous carbon, having a nearly straight frac- 

 ture, burning with facility, and presenting many of the cha- 

 racters of true coal. None of the exterior characters of lig- 

 nite are observable in these varieties. But their manner of 

 burning, the odour then emitted, — and what is better than this, 

 the considerable mass of ligneous stems, some perfecriy recog- 

 nisable and scarcely changed, others so much altered that the 

 ligneous structure has almost entirely disappeared, are facts 

 which leave no doubt on the origin of this mass of fossil com- 

 bustibles. The absence of every vegetable of the Fern family, 

 and of all others belonging to the ancient coal formation, are 

 negative characters, which, added to the former, contribute to 

 distinguish this formation from the coal measures. 



Plastic clay, i. e. non-effervescent and infusible, is found be- 

 neath the lignite ; that occurring between the beds of lignite 

 is sandy and less pure, and is sometimes accompanied by beds 

 of sandstone ; so that the relations of the two clays to each 

 other is the same here as on the plateau of Arcueil and Van- 

 vres near Paris, — a circumstance which completes the charac- 

 ters of this formation. It is in this clay that the spathose 

 nacreous limestone named Schauvierde occurs ; and it is from 

 the same clay, worked at the foot of the hill, near the village 

 of Grossalmerode, that the celebrated Hessian crucibles are 

 made. 



This formation is covered at Mount Meissner by a mass of 

 basalt, celebrated on account of the discussions that have taken 

 place respecting its origin. 



8. Observations on the Porphyry ofTceplitz, and the Clinkstone 

 of the Schlossberg ; by Dr. C. Naumann*. 



The Mittelgebirge appears, says the author, to have been 

 the central situation of those great eruptions which have prin- 

 cipally acted along the southern side of the Erzgebirge, and 



• From a notice in Baron de Ferussac's Bull, des Sciences, for June, 

 1826, of the memoir contained in Leonhnrd's Zeitschrift fur Mineralogie, 

 Oct. 1825. 



which 



